The technical field of this invention is methods for cleaning and maintaining electrodes used in electroplating apparatus used in the electroplating of metals onto semiconductor workpieces.
In the production of semiconductor wafers and other semiconductor articles it is necessary to plate metals onto the semiconductor surface to provide conductive areas which transfer electrical current. There are two primary types of plating layers formed on the wafer or other semiconductor workpiece. One is a blanket layer used to provide a metallic layer which covers large areas of the wafer. The other is a patterned layer which is discontinuous and provides various localized areas that form electrically conductive paths within the layer and to adjacent layers of the wafer or other device being formed.
The plating of copper onto semiconductor articles has in particular proven to be a great technical challenge and at this time has not achieved commercial reality due to practical problems of forming copper layers on semiconductor devices in a reliable and cost efficient manner.
In the electroplating of copper, aluminum, tin, nickel, and other metals there is a reoccurring problem of buildup of the metal being plated on the electrodes. In typical processes the anode is present in the plating bath and the cathode is connected to the wafer or other semiconductor article being plated. Deposits of the plating metal occur not only on the wafer but also at the cathodes. When these deposits of plating metal become substantial, then they must be removed. Removal is needed to prevent unintended attachment of the electrodes to the wafer being plated, and to prevent small particles of plating metal from breaking free and lodging on the wafer in a local which results in a defect.
Under prior knowledge it has been it has been necessary to remove the deposits from the cathodes on a frequent basis using a manual maintenance procedure. The prior techniques have required manual removal of the cathodes from the processing equipment with associated cleaning and reinstallation back into the processing equipment. Such maintenance requirements have a very derogatory effect on production throughput because the machine is shut down and service is then performed. Even if the maintenance allows installation of new or substitute electrodes, the down-time is substantial and a significant economic loss for the semiconductor device manufacturer.
Thus, there is a need in the art for improved techniques, apparatus, and maintenance procedures for removing accumulated plating deposits from the electrodes of semiconductor plating systems.